Generally, energy consumption relating to air-conditioning occupies a half of energy consumption for all building equipments. Therefore, promotion of energy saving for air-conditioning highly contributes to energy saving for entire of building equipments.
Meanwhile, it is required to satisfy sensation of warmth (i.e. comfort) of persons in an amenity space such as a room in a business building. Though ensuring comfort has aspects opposing against energy saving, energy waste can be saved by restraining excessive energy consumption beyond a range where persons in a room feel comfortable.
Therefore, a control using a comfort index called as PMV is widely adopted for contamination of comfort and energy saving. Hereinafter, the comfort index “PMV” will be explained.
The PMV is a comfort index calculated by use of parameters (a) air temperature, (b) relative humidity, (c) mean radiant temperature, (d) airflow speed, (e) activity index value [index of heat generation within human body], and (f) amount of clothing that affects a human sensation of warmth with respect to heat and cold.
An amount of heat generation in a human is a sum of an amount of convective radiation, an amount of heat radiation in heat radiation, an amount of evaporative heat, an amount of heat radiation through breathings, and an amount of stored heat. When an equation of thermal equilibrium with respect to these is satisfied, a human body is thermally neutral and in a comfortable state that is not too hot and too cold. On the other hand, a human body feels heat and cold when the equation of thermal equilibrium becomes invalid.
Professor Fanger at the Technical University of Denmark released an introduction of a comfort equation in 1967. This being as a start point, a thermal load to a human body and a human sensation for heat and cold were associated each other through statistical analyses of questionnaires to many European and American examinees, so that the PMV (Predicted Mean Vote) was proposed. This was got into the ISO standard and then frequently used in recent days.
The PMV as an index of sensation of heat and cold is presented with a value using next seven-grade evaluation scale.
+3 Hot
+2 Warm
+1 Slightly warm
0 Neutral
−1 Slightly cool
−2 Cool
−3 Cold
Among the above-mentioned parameters, the activity index value that represents work intensity is generally used with a unit of a metabolism amount “met”, and the amount of clothing is used with a unit “clo”.
The unit “met” represents a metabolism amount and 1 met is defined with a following equation (1) based on a metabolism amount under resting condition in a thermally comfort state.1 met=58.2 W/m2=50 kcal/m2·h  (1)
In addition, the unit “clo” represents a thermally insulation property of clothing and 1 clo is a value such that an amount of heat radiation from a surface of a human body in a room (21° C. of air temperature, 50% of relative humidity and not more than 5 cm/s of airflow speed) equilibrates with a metabolic amount of 1 met. It is defined with a following equation (2) based on a conversion to a normal thermal resistance value.1 clo=0.155 m2·° C./W=0.18 m2·h·° C./kcal  (2)
An air-conditioning load can be reduced to save energy by setting a PMV target value within a comfortable range (−0.5<PMV<+0.5) using a following equation (3) so that it is set toward a hot side when cooling or toward a cold side when heating.PMV=(0.352e−0.042M/A+0.032)·L  (3)
M: activity index value [kcal]
A: surface area of human body [m2]
L: thermal load to human body [kcal/m2·h] (calculated from the Fanger's comfort equation)
e: base of natural logarithm
A patent document 1 (Japanese Patent Application Laid-opened No. 2006-331372) discloses environmental energy management system that achieves energy saving while ensuring comfort of persons in a room using the PMV and so on. The system is configured with an apparatus to which an agent technique is applied. The system achieves both of optimization of indoor thermal environment and minimization of energy consumption according to a control function for air-conditioning equipments based on functions of the agent apparatus (i.e. an autonomous control function, a logical group function, and a hierarchization function) and functions of a management apparatus (i.e. a data acquisition function from the agent apparatus, an integrated management/control function for the agent apparatus, and a calculation function of the thermal environment and the energy optimization).